Actually when your head is done in, even the sound of it ringing or a text popping up is enough to drive a person mad. It's also a lot easier when overwhelmed to just hit the off switch than to fiddle around with settings so only certain notifications pop up or only calls from certain people get through.
It's also not about choosing whether to respond to a text or missed call. It's about the pressure of knowing you have one. It's about having to read the contents of a text to be able to decide whether or not to respond.
It's about picking up a text or voicemail from some worrier and wanting to reassure them (because they're worried and you're not an arsehole) but simultaneously not wanting to communicate with anyone at all for any reason and needing to be left alone.
It's about being able to recover from feeling overwhelmed, not prolonging it due to all these well-meaning but anxious people who just can't accept that someone doesn't want to talk right now and expects you to fix their anxiety for them by responding in some way.
It's knowing that CuntyMcCunt-Face has texted wanting a CF favour and knowing that they'll be annoyed you didn't respond or when you do respond saying no. Stressing you out further at a time you just want peace.
It's knowing that both CuntyMcCunt-Face and MsWorry-Wort will keep texting or phoning until they get a response, meaning you just can't relax.
Sometimes switching off the phone is the only way to get the peace you need. It's not dramatic. It's not being done for effect or to generate feelings-of-whatever in other people or to manipulate them in any way. It's just some people's chosen way of successfully managing their own lives and emotional state. It's not about other people, its about the owner of the phone. What's dramatic about self-sufficiently making your own life work for you?